This invention is concerned with couplings of the type shown and described in U.S. Pat. Nos. 3,521,910 and 5,145,219. These patents are incorporated herein by reference and describe tube couplings wherein first and second coupling components or glands with central through passages or bores are disposed in mating relation. Particularly, end faces include annular raised beads arranged to sealingly engage on opposite sides of an annular metal gasket. A threaded nut assembly acts to drive the end faces toward each other and cause the beads to sealingly engage the gasket. The sealing end faces can be located on separate glands or on a "block", e.g. a face of a fluid component such as a valve, regulator, etc.
Commercially successful versions of this type of coupling assembly require a desired amount of compression of the sealing end faces on opposite sides of the gasket. This is achieved by design of the components and instructing the user to rotate the nut assembly a predetermined amount. Because of the pitch of the thread and the design of the individual components, a desired compression is thus achieved.
In order to eliminate the potential for over tightening by the user, it has been suggested that a restraint be provided to limit the amount of compression imposed on the seal gasket. For example, U.S. Pat. No. 5,482,332 provides axial projections adapted to engage one another and limit the potential for over tightening.
Still another concern with the face seals of this general type is relative movement between the end face seals and the gasket. In order that a precise seal be formed, it is desired that the gasket be locked into place relative to end faces and that the end faces be axially advanced toward one another and into sealing engagement with opposite faces of the gasket.
It is also desired that the sealed relationship between the gasket and the respective glands be maintained even if torque is applied to the fitting after make-up. For example, if torque is applied to a tube end while the remainder of the coupling assembly is held in place, then there is a concern that the seal may be compromised.
Still another issue associated with these coupling assemblies is the requirement for ultra-high purity. That is, the ultra-clean environment associated with these types of fluid components requires elimination of minute particles that might otherwise be ignored in less demanding environments. Any opportunity to decrease the prospect for particle generation is desired.
The present invention contemplates a new and improved coupling assembly that overcomes all of the above referenced problems and others and provides positive stop feedback, resists torque and elimination of relative motion between mating components, and increases the resistance of the coupling assembly to loosening.